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Earlier today I tried--at least the best I could--to explain the nature of why jump starts on the 3.6L are the way they are, and particularly what happens when:
https://www.jlwranglerforums.com/forum/threads/why-3-6l-jumpstarts-are-the-way-that-they-are.27758/
I'm going to do my best not to rehash that, but revisit a few factual points from that post needed to understand this thread.
Some more necessary points:
It is the facts above that are making me theorize (I could be wrong!!) that the reason so many people report portable power packs failing with the JL is that when hooked up to the 3.6L JL's main (or either) battery, (as per the manual) they first charge both batteries (given those batteries are connected in parallel,) the pack gets depleted somewhat in the process, and then these portable packs take on their classic jump start role of energizing the starter, possibly lacking the power to turn over the engine having lost power during the prior "charge and wait" phase of the 3.6L jump starting process: which is really a "charge and then jump start" process.
These portable devices are typically great a delivering lots of current quickly. Charging batteries for a few minutes, as required here, and then cranking the engine, may not be "their calling."
But, imagine the following. You're stranded in the middle of nowhere with your 1) charged power pack, and 2) a socket wrench and your metric bolts. What if you:
Here's why I theorize it ***might*** work.
There are content specialists on the board who live this stuff. I would love to hear from them why they think this might or might not work. : - )
Peace.
- We wait on the donor vehicle's battery (not really) and why, and
- Why possibly, portable and fully charged self contained charging devices and the JL don't get along well.
https://www.jlwranglerforums.com/forum/threads/why-3-6l-jumpstarts-are-the-way-that-they-are.27758/
I'm going to do my best not to rehash that, but revisit a few factual points from that post needed to understand this thread.
- At rest, and most other times, your 3.6L's batteries are connected in parallel. Because of this, charge or use one battery, and you charge and use the other.
- From the factory, whenever the engine cranks, the starter, while getting its power from both batteries, is "told" to do "its thing" from a starter relay which solely depends on the ESS battery for its power.
Some more necessary points:
- When you jump start the 3.6L and put the jumper cables of another vehicle on the main battery and wait, just as you should, you are charging both batteries, but most importantly the ESS battery, which, when you press the JL's engine Start button and brake pedal, is going to result in a situation where the ESS battery has to have enough juice, all on its own, to energize the starter relay to signal the starter.
- The ESS battery is all on its own here because for a brief instant before the engine cranks (and during an ESS event) the two batteries are isolated. Why FCA did this is discussed in the other thread.
It is the facts above that are making me theorize (I could be wrong!!) that the reason so many people report portable power packs failing with the JL is that when hooked up to the 3.6L JL's main (or either) battery, (as per the manual) they first charge both batteries (given those batteries are connected in parallel,) the pack gets depleted somewhat in the process, and then these portable packs take on their classic jump start role of energizing the starter, possibly lacking the power to turn over the engine having lost power during the prior "charge and wait" phase of the 3.6L jump starting process: which is really a "charge and then jump start" process.
These portable devices are typically great a delivering lots of current quickly. Charging batteries for a few minutes, as required here, and then cranking the engine, may not be "their calling."
But, imagine the following. You're stranded in the middle of nowhere with your 1) charged power pack, and 2) a socket wrench and your metric bolts. What if you:
- Disconnect the leads to both terminals on the main battery, and
- Disconnect, on these leads, the two cables (one positive, one negative) that lead to the ESS battery. On the negative lead I think it the cable closer to the main battery's negative post, and on the positive side I think it the cable closest to the firewall.
- Now take these disconnected cables and hook them up to your power pack directly, and try to start the rig up. No waiting (I theorize) required.
Here's why I theorize it ***might*** work.
- For the brief time between hooking up your power pack to these loose cables and trying to start the 3.6 JL you'll only be charging the ESS battery.
- When you try to crank the JL without waiting much, the ESS battery may lack sufficient charge, but its got the powerpack to help it. Not so with the classic jump start connection to the main battery method, which, along with your donor power, is isolated during crank from the ESS battery.
- Once, if my theory holds true, the engine cranks, hook back up the ESS cables to their leads, and those leads to the main battery's posts like you found it. Of course be careful. Your (working) alternator will take over charging from here now that the engine's on.
There are content specialists on the board who live this stuff. I would love to hear from them why they think this might or might not work. : - )
Peace.
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